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from .utils import *
# common instructions all push commands end with
PUSH_COMMON_ASM = """@SP
A=M
M=D
@SP
M=M+1
"""
# push <segment> <index>
# when <segment> is one of local, argument, this and that
PUSH_ASM = (
"""@{segment}
D=M
@{index}
A=D+A
D=M
"""
+ PUSH_COMMON_ASM
)
# when <segment> is one of static, temp and pointer
PUSH_FIXED_ASM = (
"""@{addr}
D=M
"""
+ PUSH_COMMON_ASM
)
# push constant <constant>
PUSH_CONSTANT_ASM = (
"""@{constant}
D=A
"""
+ PUSH_COMMON_ASM
)
# pop <segment> <index>
# when <segment> is one of local, argument, this and that
POP_ASM = """@{index}
D=A
@{segment}
M=M+D
@SP
AM=M-1
D=M
@{segment}
A=M
M=D
@{index}
D=A
@{segment}
M=M-D
"""
# when <segment> is one of static, temp and pointer
POP_FIXED_ASM = """@SP
AM=M-1
D=M
@{addr}
M=D
"""
SEGMENT_PTR = {
"local": "LCL",
"argument": "ARG",
"this": "THIS",
"that": "THAT",
}
SEGMENT_SIZE = {
"pointer": 2, # 3..4, i.e. THIS and THAT
"temp": 8, # 5..12
"static": 240, # 16..255
}
def translate_memory(action, segment, index, prog, verbose=False):
try:
index = int(index)
except ValueError:
exit_on_error(
f"Syntax error: invalid segment index {index}", EXIT_CODE_SYNTAX_ERROR
)
if index < 0:
exit_on_error(
f"Address error: negative segment index {index}", EXIT_CODE_ADDR_ERROR
)
asm = f"// {action} {segment} {index}\n" if verbose else ""
if segment in ["local", "argument", "this", "that"]:
# these segments are dynamic
asm += PUSH_ASM if action == "push" else POP_ASM
asm = asm.format(segment=SEGMENT_PTR[segment], index=index)
elif segment in ["static", "temp", "pointer"]:
# these segments have a fixed location and size on memory
if index >= SEGMENT_SIZE[segment]:
exit_on_error(
f"Address error: segment index {index} exceeds size of {segment}",
EXIT_CODE_ADDR_ERROR,
)
addr = ""
if segment == "static":
# translate "static i" in "prog.vm" into "@prog.i"
addr = f"{prog}.{index}"
elif segment == "temp":
addr = str(5 + index)
else:
# "pointer 0" is THIS, "pointer 1" is THAT
addr = "THIS" if index == 0 else "THAT"
asm += PUSH_FIXED_ASM if action == "push" else POP_FIXED_ASM
asm = asm.format(addr=addr)
elif segment == "constant":
if action == "pop":
exit_on_error(
f"Syntax error: popping to constant not allowed", EXIT_CODE_SYNTAX_ERROR
)
asm += PUSH_CONSTANT_ASM.format(constant=index)
else:
exit_on_error(
f"Syntax error: invalid memory segment {segment}", EXIT_CODE_SYNTAX_ERROR
)
return asm
|
